Heretofore, a high-class molded article whose appearance and soft feeling are enhanced by laminating a skin material on a thermoplastic resin molded article has widely been known. As the skin material, there has been used soft polyvinyl chloride backed with a foam layer of polyolefin, polyurethane resin, etc. to impart cushioning characteristics. Examples of a method of producing a laminated molded article with the skin include a method in which a molded article is obtained by firstly molding a thermoplastic resin according to various molding methods such as injection molding, etc. and then molding a skin material on the molded article by vacuum molding, and a method of adhesion-laminating using an adhesive while simultaneous molding is conducted.
However, it has been known that the above methods have the following drawbacks.
The polyvinyl chloride skin material has a large specific gravity and it is inferior in light resistance. When using it as a skin material of a component exposed to the direct rays of the sun, severe deterioration of surface appearance and feeling occurs. Since the polyvinyl chloride skin material is softened by adding a large amount of a plasticizer, there arose a problem that a front glass becomes dim due to an influence of the plasticizer when using it as an interior automotive trim.
There is also a problem that polyvinyl chloride evolves a hydrogen chloride gas when it is burned and, therefore, disposal of the waste by incineration often causes environmental sanitation or a problem of corroding various processing equipment.
According to the method using an adhesive, the process becomes complicated and the cost becomes high. Further, this method has a problem of environmental pollution due to a solvent, a dispersant, etc. which are used for the adhesive.
In order to solve the above problems, a polyolefin elastomer skin is suggested as the skin material in place of the polyvinyl chloride skin. Using the polyolefin elastomer skin, however, often causes molding failure.
A lamination integral molding of the skin and thermoplastic resin is also suggested as an improved method for production (e.g. JP-A-4-73112). That is, JP-A-4-73112 discloses that the above-mentioned molding failure is solved by a method which comprises disposing a laminated skin material, which comprises an olefin thermoplastic elastomer sheet backed with a foam layer, between non-closed male and female molds, feeding a molten thermoplastic resin between the foam layer and the male or female mold, and putting the male and female molds together to integrally laminate the skin material and thermoplastic resin, controlling the tensile strength of the thermoplastic elastomer and the friction resistance between the thermoplastic elastomer and a metal surface.
In these methods, however, collapse and break of the foam can not be completely prevented, depending on the thickness, constitution ratio, contents and the like of the thermoplastic elastomer sheet and foam. That is, a thinner thermoplastic elastomer layer is tend to be used recently for cost reduction and the above-mentioned failure sometimes arise even if using a thermoplastic elastomer which has imparted a good appearance heretofore.